Diaper rash is a common form of irritation and inflammation of those parts of an infant's body normally covered by a diaper. This condition is also referred to as diaper dermatitis, napkin dermatitis, napkin rash, and nappy rash. While certainly more common in infants, this condition is not, in fact, limited to infants. Any individual who suffers from incontinence may develop this condition. This ranges from newborns, to the elderly, to critically ill or nonambulatory individuals.
It is generally accepted that true "diaper rash" or "diaper dermatitis" is a condition which is, in its most simple stages, a contact irritant dermatitis. The irritation of simple diaper rash results from extended contact of the skin with urine, or feces, or both. Diapers are worn to catch and hold the body waste, but generally hold the waste in direct contact with the skin until changed, i.e., in occluded fashion for long periods of time. The same is true for an incontinence pad, or incontinence brief. However, while it is known that the body waste "causes" diaper rash, the precise component or components of the urine or feces which are responsible for the resulting irritation of the skin have not been conclusively identified. The most commonly accepted list of factors linked to diaper rash includes ammonia, bacteria, the products of bacterial action, urine pH, Candida albicans, and moisture. These are generally cited in the art as being the most likely candidates for agents or conditions which produce or aggravate diaper rash.
It has now been discovered that a primary cause of diaper rash is a particular set of conditions which arises as a result of prolonged contact of skin with mixtures of feces and urine. Activity of proteolytic and lipolytic fecal enzymes present in such a mixture is believed to be a major factor in producing skin irritation. Urine in contact with enzymes from feces can also result in production of ammonia which raises skin pH. This rise in skin pH, for example to levels of 6.0 and above, in turn increases that fecal proteolytic and lipolytic enzymatic activity which produces diaper rash. Urine itself can also contribute to diaper rash by adding moisture to the diaper environment. Water, and particularly water in the form of urine, is especially effective at diminishing the barrier property of skin, thereby enhancing the susceptibility of skin to fecal enzyme irritation. However, when skin pH is kept between about 3.0 and 5.5, the skin's barrier properties can be maintained. The foregoing diaper rash model suggests that effective diaper rash control can be achieved by maintaining skin pH well within the acidic range to inhibit irritation-producing enzymatic activity while simultaneously maintaining the diaper environment as dry as possible.
Articles, compositions and procedures which inherently tend to lower the pH of diapered skin are known in the art. In fact, a number of prior art references teach the addition of various acidic pH control or "ammonia-absorbing" agents to diapers or to the diapered skin environment. Such references include, for example, Alonso et al., U.S. Pat. No. 4,382,919, Issued May 10, 1983; Blaney, U.S. Pat. No. 3,964,486, Issued June 22, 1976; Bryce, U.S. Pat. No. 3,707,148, Issued Dec. 26, 1972; and Jones, Sr., U.S. Pat. No. 3,794,034, Issued Feb. 26, 1974.
Likewise, a number of prior art references describe absorbent articles which are said to be especially effective in absorbing urine and maintaining skin dryness. Frequently such articles involve the utilization of superabsorbent polymeric material, such as water-insoluble, slightly cross-linked hydrogel or hydrocolloid material, that absorbs and holds many times its weight in discharged fluid. References involving the use of such superabsorbent polymers in diaper structures include, for example, Harper et al., U.S. Pat. No. 3,669,103, Issued June 13, 1972; Harmon, U.S. Pat. No. 3,670,731, Issued June 20, 1972; Masuda et al., U.S. Pat. No. 4,076,663, Issued Feb. 28, 1978; Melican, U.S. Pat. No. 4,232,674, Issued Nov. 11, 1980; Holtman, U.S. Pat. No. 4,333,463, Issued June 8, 1982; Mazurak et al., U.S. Pat. No. 4,381,782, Issued May 3, 1983 and Elias, U.S. Pat. No. 4,381,783, Issued May 3, 1983.
None of the foregoing prior art references provide both especially effective skin pH control agents and especially effective moisture-absorbing hydrogel polymers in the same absorbent structure. In fact, simple combination of acidic pH control agents with superabsorbent polymer material in the same structure cannot be accomplished without some difficulty. The preferred moisture-absorbing hydrogel materials are not especially effective fluid absorbers under low pH conditions. The presence of acidic skin pH control agents, which lower pH conditions in the region of hydrogel-moisture contact, thus tends to diminish the moisture-absorbing effectiveness of the hydrogel materials. There is therefore a need to identify preferred structures and configurations for absorbent articles which contain both effective acidic pH control agents and effective moisture-absorbing hydrogel polymers such that each of these components can efficiently contribute to the prevention or reduction of diaper rash. It has not been discovered that improved diaper rash-reducing absorbent articles containing both acidic pH control agents and moisture-absorbing, highly neutralized hydrogel can be realized by incorporating these materials into distinct zones or areas within the absorbent article structure.